Subzero: Fix address mode optimization involving phi temporaries.

src/IceCfgNode.cpp

 //===- subzero/src/IceCfgNode.cpp - Basic block (node) implementation -----===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the CfgNode class, including the complexities
@@ skipping 149 matching lines @@
       InstAssign *NewInst = InstAssign::create(Func, Dest, Operand);
       // If Src is a variable, set the Src and Dest variables to
       // prefer each other for register allocation.
       if (Variable *Src = llvm::dyn_cast<Variable>(Operand)) {
         bool AllowOverlap = false;
         Dest->setPreferredRegister(Src, AllowOverlap);
         Src->setPreferredRegister(Dest, AllowOverlap);
       }
       Insts.insert(InsertionPoint, NewInst);
       NewInst->updateVars(this);
+      Dest->resetDefinition();

[jvoung (off chromium), 2014/08/27 16:21:07]

This is a way to indicate that the Dest variable is now multi-block?

[Jim Stichnoth, 2014/08/27 20:23:14]

It's more about indicating Dest is multi-def, to prevent address mode
optimization from following definitions across phis.

With that said, I think it's probably better to make this more automatic inside
setDefinition(), so I reverted this resetDefinition() function.

     }
   }
 }
 
 // Deletes the phi instructions after the loads and stores are placed.
 void CfgNode::deletePhis() {
   for (PhiList::iterator I = Phis.begin(), E = Phis.end(); I != E; ++I) {
     (*I)->setDeleted();
   }
 }
@@ skipping 323 matching lines @@
          I != E; ++I) {
       if (I != OutEdges.begin())
         Str << ", ";
       Str << "%" << (*I)->getName();
     }
     Str << "\n";
   }
 }
 
 } // end of namespace Ice